The present invention generally relates to disk units and portable electronic equipment, and more particularly to disks unit and a portable electronic equipment which have a high reliability with respect to change in operating environment in which the disk units and the portable electronic equipment are used.
Recently, due to the increased amount of information processing in computer systems or the like, the amount of information written to and read from a magnetic disk unit has also increased, thereby increasing the memory capacity of the magnetic disk unit. On the other hand, in a magnetic disk unit used in a portable electronic equipment such as a lap-top personal computer, there are demands not only to increase the memory capacity, but also to reduce the size of the equipment and to enable easy operation of the equipment under various operating environments.
Conventionally, the magnetic disk unit was used under an operating environment which is restricted to a certain extent, such as in a computer room or on a desk top within an office. However, the size and weight of the electronic equipments such as the personal computer have been reduced considerably, resulting in more opportunities for the magnetic disk unit to be used under various operating environments.
Environmental factors affecting the reliability of the magnetic disk unit include the atmospheric pressure, temperature, humidity and the like. For example, the atmospheric pressure changes from that under the normal operating environment when the magnetic disk unit is used at a high-altitude location or within an airplane during flight.
The magnetic disk unit generally includes a magnetic disk which stores information, a magnetic head which writes information to and reads information from the magnetic disk, a positioning mechanism which moves the magnetic head to a desired position on the magnetic disk, and a motor which rotates the magnetic disk. When the environmental factors such as those described above change, the floating distance of the magnetic head from the magnetic disk decreases within the magnetic disk unit, and the possibility of the magnetic head contacting the magnetic disk increases. If the contact between the magnetic head and the magnetic disk is repeated over a long period of time, the magnetic head and the magnetic disk become damages, and the so-called head crash occurs whereby the information written on the magnetic disk is also destroyed.
The temperature and humidity under the operating environment of the magnetic disk unit are limited to certain ranges since the user who uses the magnetic disk unit can only work under limited environmental conditions. For this reason, it is unlikely that the magnetic disk unit will be used under extreme temperature and humidity conditions for a long period of time. However, the atmospheric pressure under which the magnetic disk unit is used may vary considerably. The atmospheric pressure at a high-altitude location or within the airplane during flight may vary in a range of approximately 0.7 to 0.8 standard atmosphere (atm), and the magnetic disk unit is often used under such pressure ranges. The atmospheric pressure greatly affects the floating distance of the magnetic head from the magnetic disk. Therefore, in addition to measures taken against temperature and humidity changes, it is desirable to take measures against the change in the atmospheric pressure.
Conventionally, various measures have been proposed against the change in the atmospheric pressure. A Japanese Laid-Open Patent Application No.54-614 proposes a method of adjusting the atmospheric pressure within the magnetic disk unit by providing a pressure adjusting bag. A Japanese Laid-Open Patent Application No.55-48866 proposes a method of controlling and stabilizing the pressure within the magnetic disk unit by providing a mechanism for controlling the mass of air flow. A Japanese Laid-Open Patent Application No.58-16837 proposes a method of balancing the pressure within the unit and the open air by use of an expanding and contracting bag. A Japanese Laid-Open Patent Application No.63-117378 proposes a method of providing an air pump which variably adjusts the pressure within the magnetic disk unit so that the shock when a magnetic head slides on a magnetic disk is reduced by increasing the pressure when stopping the rotation of the magnetic disk. A Japanese Laid-Open Patent Application No.2-260183 proposes a method similar to that proposed in the Japanese Laid-Open Patent Application No.63-117378. A Japanese Laid-Open Patent Application No.63-195893 proposes a method of providing a gas cylinder containing a high-pressure gas, so as to enable use of the unit under a low-pressure environment. In addition, a Japanese Laid-Open Patent Application No.5-74129 proposes a method of suppressing a pressure difference from being generated between the inside and the outside of the unit by using a bellows structure or a resilient body.
Basically, according to the above described units which have been proposed, a mechanism such as a pressure adjusting mechanism is additionally provided with respect to the unit, so as to return the operating environment to the original operating environment when the operating environment changes or, to minimize the change in the operating environment.
However, if an additional mechanism such as the pressure adjusting mechanism were provided on the magnetic disk unit, it would increase both the size and weight of the magnetic disk unit. As a result, it would be impossible to cope with the demands to reduce both the size and weight of the magnetic disk unit.
Also, if the additional mechanism such as the pressure adjusting mechanism were provided on the magnetic disk unit, it would increase the power consumption of the magnetic disk unit because the pressure adjusting mechanism or the like has a relatively large power consumption. As a result, it would be impossible to cope with the demands to reduce the power consumption of the portable electronic equipment which uses the magnetic disk unit.